<html>
<META http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<head>
<title>Section 20.1.&nbsp; Introduction</title>
<link rel="STYLESHEET" type="text/css" href="images/style.css">
<link rel="STYLESHEET" type="text/css" href="images/docsafari.css">
</head>
<body>
<table width="100%" border="0" cellspacing="0" cellpadding="0">
<tr><td><div STYLE="MARGIN-LEFT: 0.15in;"><a href="toc.html"><img src="images/team.gif" width="60" height="17" border="0" align="absmiddle"  alt="Team BBL"></a></div></td>
<td align="right"><div STYLE="MARGIN-LEFT: 0.15in;">
<a href=ch20.html><img src="images/prev.gif" width="60" height="17" border="0" align="absmiddle" alt="Previous Page"></a>
<a href=ch20lev1sec2.html><img src="images/next.gif" width="60" height="17" border="0" align="absmiddle" alt="Next Page"></a>
</div></td></tr></table>
<br><table width="100%" border="0" cellspacing="0" cellpadding="0"><tr><td valign="top"><a name="ch20lev1sec1"></a>
<h3 class="docSection1Title">20.1. Introduction</h3>
<p class="docText"><a name="idd1e148423"></a><a name="idd1e148426"></a><a name="idd1e148431"></a><a name="idd1e148436"></a><a name="idd1e148439"></a><a name="idd1e148442"></a><a name="idd1e148445"></a><a name="idd1e148448"></a><a name="idd1e148451"></a>During the early 1980s, the UNIX System was considered a hostile environment for running multiuser database systems. (See Stonebraker [<a class="docLink" href="bib01.html#biblio01_060">1981</a>] and Weinberger [<a class="docLink" href="bib01.html#biblio01_066">1982</a>].) Earlier systems, such as Version 7, did indeed present large obstacles, since they did not provide any form of IPC (other than half-duplex pipes) and did not provide any form of byte-range locking. Many of these deficiencies were remedied, however. By the late 1980s, the UNIX System had evolved to provide a suitable environment for running reliable, multiuser database systems. Since then, numerous commercial firms have offered these types of database systems.</P>
<p class="docText">In this chapter, we develop a simple, multiuser database library of C functions that any program can call to fetch and store records in a database. This library of C functions is usually only one part of a complete database system. We do not develop the other pieces, such as a query language, leaving these items to the many textbooks on database systems. Our interest is the UNIX System interface a database library requires and how that interface relates to the topics we've already covered (such as recordbyte-rangelocking, in <a class="docLink" href="ch14lev1sec3.html#ch14lev1sec3">Section 14.3</a>).</P>

<ul></UL></TD></TR></table>
<table width="100%" border="0" cellspacing="0" cellpadding="0">
<tr><td><div STYLE="MARGIN-LEFT: 0.15in;"><a href="toc.html"><img src="images/team.gif" width="60" height="17" border="0" align="absmiddle"  alt="Team BBL"></a></div></td>
<td align="right"><div STYLE="MARGIN-LEFT: 0.15in;">
<a href=ch20.html><img src="images/prev.gif" width="60" height="17" border="0" align="absmiddle" alt="Previous Page"></a>
<a href=ch20lev1sec2.html><img src="images/next.gif" width="60" height="17" border="0" align="absmiddle" alt="Next Page"></a>
</div></td></tr></table>
</body></html><br>
<table width="100%" cellspacing="0" cellpadding="0"
style="margin-top: 0pt; border-collapse: collapse;"> 
<tr> <td align="right" style="background-color=white; border-top: 1px solid gray;"> 
<a href="http://www.zipghost.com/" target="_blank" style="font-family: Tahoma, Verdana;
 font-size: 11px; text-decoration: none;">The CHM file was converted to HTM by Trial version of <b>ChmD<!--158-->ecompiler</b>.</a>
</TD>
</TR><tr>
<td align="right" style="background-color=white; "> 
<a href="http://www.etextwizard.com/download/cd/cdsetup.exe" target="_blank" style="font-family: Tahoma, Verdana;
 font-size: 11px; text-decoration: none;">Download <b>ChmDec<!--158-->ompiler</b> at: http://www.zipghost.com</a>
</TD></tr></table>
